Like other abiotic stresses, salt stress has become a major factor that restricts the growth, distribution and yield of crops. Research has shown that increasing the nitrogen content in soil can improve the salt tolerance of plants and nitrate transporter (NRT) is the primary nitrogen transporter in plants. Suaeda salsa (L.) Pall is a strong halophyte that can grow normally at a salt concentration of 200 mM. The salt stress transcriptome database of S. salsa was found to contain four putative genes that were homologous to NRT, including SsNRT1.1A, SsNRT1.1B, SsNRT1.1C and SsNRT1.1D. The cDNA of SsNRT1.1s was predicted to contain open reading frames of 1791, 1782, 1755 and 1746 bp, respectively. Sequence alignment and structural analysis showed that the SsNRT1.1 amino acids were inducible by salt and have conserved MFS and PTR2 domains. Subcellular localization showed they are on the endoplasmic reticulum. Overexpression of SsNRT1.1 genes in transgenic Arabidopsis improves its salt tolerance and SsNRT1.1C was more effective than others. We constructed a salt-stressed yeast cDNA library and used yeast two-hybrid and BiFC technology to find out that SsHINT1 and SsNRT1.1C have a protein interaction relationship. Overexpression of SsHINT1 in transgenic Arabidopsis also improves salt tolerance and the expressions of Na⁺ and K⁺ were increased and reduced, respectively. But the K⁺/Liratio was up-regulated 11.1-fold compared with the wild type. Thus, these results provide evidence that SsNRT1.1C through protein interactions with SsHINT1 increases the K⁺/Na⁺ ratio to improve salt tolerance and this signaling may be controlled by the salt overly sensitive (SOS) pathway.

The nitrate signaling core regulator NLP7 is known to negatively regulate salt tolerance in Arabidopsis thaliana, but the function of the (SsNLP7A) gene in the halophyte Suaeda salsa remains unclear. To investigate whether SsNLP7A participates in salt stress responses, this study heterologously overexpressed the gene in tomato (Solanum lycopersicum) and systematically evaluated its function under salt stress through phenotypic, physiological, and transcriptomic analyses. The results indicate that SsNLP7A overexpression significantly promotes tomato root development and alleviates growth inhibition caused by salt stress. Under salt treatment, transgenic plants exhibited significantly higher chlorophyll content, accumulation of osmotic regulators (proline and soluble sugars), and antioxidant enzyme (POD, CAT, SOD) activity compared to wild-type plants. Transcriptome analysis further revealed that SsNLP7A enhances salt tolerance by regulating carbon metabolism, phytohormone signaling pathway, photosynthesis, and antioxidant pathways. Collectively, this study elucidates the positive regulatory role of SsNLP7A in salt stress response, providing new insights into its molecular mechanisms.